Adding a ground to abandonded 3 wire 220?

Reply

  #1  
Old 10-21-07, 03:33 PM
Member
Thread Starter
Join Date: Oct 2006
Location: Now in Sun City, AZ
Posts: 134
Question Adding a ground to abandonded 3 wire 220?

This is in AZ by the way.....

I have a "potential" 3 wire circuit availble for use in the attached garage. It is to a 220/30amp dryer recepticle that was 'abandoned' when the dryer was located over to the right and a new circuit put in over there. My best estimate at the moment is that the existing wire is probably 8 ga stranded aluminium. ( The "abandoned" wire is curled up in the bottom of the main breaker box, begging to be used...)

What I would like to do is utilize this wire to add a small subpanel to supply 2 - 3 circuits in the garage for various use ( radial arm saw, old shopsmith, shop vac, etc) on 2 circuits, and put the garage lights on their own separate circuit.

However, I gather that I would need to add a 4th ground wire to install a subpanel out there.

Can I run a separate ground wire to accomplish this?

What would be your collective opinions and options to utilize this existing wiring?
Thanks .
 
Sponsored Links
  #2  
Old 10-21-07, 04:07 PM
Member
Join Date: Sep 2002
Location: welland ontario
Posts: 5,599
You can not run a separate ground wire. Being an attached garage you must run all four wires. They must be bundled together either in one cable or in a conduit.
 
  #3  
Old 10-21-07, 08:34 PM
Member
Thread Starter
Join Date: Oct 2006
Location: Now in Sun City, AZ
Posts: 134
Well Bummer...

Could I use the 3 wires to feed a 120 circuit? That naturally would require marking one of the 2 wires as a 'white" neutral.
 
  #4  
Old 10-21-07, 08:37 PM
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
Not unless one of those wires is green or bare for its entire length, and another is white for its entire length. Not likely.
 
  #5  
Old 10-22-07, 05:36 AM
Member
Join Date: Sep 2002
Location: welland ontario
Posts: 5,599
Remarking wires less than #6 to white is not permitted.
 
  #6  
Old 10-22-07, 09:05 AM
Member
Thread Starter
Join Date: Oct 2006
Location: Now in Sun City, AZ
Posts: 134
Well - poooo

I won't pass the white wire test, I know that. Thanks guys.
 
  #7  
Old 10-22-07, 09:40 AM
Forum Topic Moderator
Join Date: Feb 2005
Location: Near Lansing, Michigan
Posts: 10,342
No go on the subpanel or 120V circuit. If the wire has a black, red and bare, you can use it for a 240V tool like an air compressor, welder or table saw. Just use a receptacle that is rated for aluminum wire.
 
  #8  
Old 10-22-07, 11:30 AM
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
I believe that there is a slight confusion here between the minimum that the code requires and the practical advice given based upon the code. I believe that a detailed examination of the code would come up with a way that would allow you to add an additional conductor to the cable that you have, and provide a way to run a subpanel. However, doing so is not _practical_, and so the _how_ of doing such an installation is not really relevant.

IMHO the effort and cost of adding an additional conductor to your current cable, in a code compliant fashion, would be nearly as much, if not significantly greater, then simply installing a new four conductor cable, of the desired capacity.

Joed: There is no requirement that all of the conductors in a _non-metallic_ cable be located in the same cable. They can be in separate cable, and it is even code legal for them to follow different paths. Probably _very_ bad design for the cables to follow different paths, but IMHO not a big deal if the cables are side by side. This, of course, doesn't help the OP, since he would need to find single conductor NM of appropriate gauge...probably more expensive that 3 conductor + ground NM.

-Jon
 
  #9  
Old 10-24-07, 09:57 AM
Member
Join Date: Jan 2005
Location: Philadelphia
Posts: 79
So if the wires not not need to be in the same conduit, are you saying that if he had an existing circut in his garage (other than this abondon one) and if it was connected directly to his main panel, he could take that circuit, remove the black and ground, then use that white wire by routing it to this new box to complete the circuit with 4 wires ? He may then be able to re-enable the original receptical by wiring back from the new circuit (if there is capacity).
 
  #10  
Old 10-24-07, 12:17 PM
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
Please note my caution above about what would be code minimum versus what would be practical. Sometimes the 'minimum' that code will let you get away with is actually more difficult and more expensive than higher quality approaches. Code will let you 'get away' with 120V subpanels, for example, but it almost never makes sense to do this.

Code permits circuit conductors to not be in the same overall sheath if the 'wiring method' is not metallic. This means that the outer sheath is not metallic. There are also additional cautions where the conductors penetrate metallic boxes. This can be quite useful, for example, if you need 12/4 cable but only have 12/2 on hand.

The OP has a circuit which is not suitable for use. If he somehow could get the appropriate additional conductor, he might be able to use the abandoned conductors. If he has _another_ circuit, with a suitably sized white conductor, and if he is willing to abandon that second circuit, he _might_ be able to somehow restore the first circuit. But note the problem: he is still left one circuit down, and now has a *******ized arrangement which with lots of work _might_ be legal. There is almost certainly no _practical_ reason to do this.

The only time that I might consider doing something like this is if I could add a new EGC to a circuit that was missing on, and then only if it was a rather heavy duty circuit. For all other situations, it is probably easier to simply run a new cable for all of the circuit conductors.

Additionally, while there is neither a code nor a signficant design issue with running two 12/2 cables side by side to serve as a 12/4 cable, if the conductors of a circuit follow _different_ paths you have a significant design issue. 'Loop area' in circuits (the ring of space created between the circuit conductors) is a source of significant EMF. Normally, the conductors are side by side, and have very small loop area. But if the conductors follow significantly different paths, you have lots of loop area and lots of EMF. Code only restricts this with metallic wiring methods, but IMHO this is very bad design in all cases.

-Jon
 
  #11  
Old 10-24-07, 07:46 PM
Member
Thread Starter
Join Date: Oct 2006
Location: Now in Sun City, AZ
Posts: 134
Wow, Thanks guys, to clarify

Unfortunately, I don't have a separate circuit 'available' inthe garage. The outlets are part of circuit #6, which supplies lights and recepticles inthe adjacent 'living" room.
I guess they didn't expect the old farts to need or use a separate circuit in the garage. Supposed to be out golfing all the time.

I'll research the cost of running an 8/3 or 6/3 to a subpanel. so I can overkill the garage wiring upgrade.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
'